Fable Anti-Churn

Purpose

fable-anti-churn is the authoritative duplicate-work and evidence-reuse prevention engine in get-fable. Powered by both a native Rust engine (crates/fable-anti-churn) and local CLI scripts, it cryptographically fingerprints work requests (RFC 8785 JCS + SHA-256), tracks reservation receipts, reuses identical prior passing evidence, blocks duplicate actions, halts repeated deterministic failures, and validates promotion proof with sub-millisecond execution. Keep material progress separate from churn. Material output can prove progress; it is not a churn dimension.

When to Use

• Before dispatching repetitive test commands, build scripts, or static analysis tools.
• Before spawning subagents, background workflows, or external tool calls.
• When an action or command fails deterministically, requiring local repair rather than blind retries.
• When evaluating candidate promotion gates (package integrity, test passing, authority verification).
• Across all lifecycle hooks (SessionStart, PreToolUse, PostToolUse, PostToolUseFailure, Stop).

When NOT to Use

• NOT to cancel or terminate the entire user task — gates only the specific duplicate local action.
• NOT as a substitute for valid code changes; once code changes, compute a typed invalidation (candidate_changed, etc.) to run anew.
• NOT to bypass real human authorization or security boundaries.